1. Field of the Invention
This invention relates to flexible contact lenses, and particularly to a lens configuration to enhance movement of the lens on the eye.
2. Background Information
When it is in place, a contact lens rests on a film of tears on the corneal surface. To promote tear circulation, and the discharge of metabolic substances and debris from beneath a contact lens, it is desirable that the lens be movable on the eye, as for example in connection with blinking. Conventional soft lenses typically move on the eye, with the blinking of the eye, through a range of about 0.1 mm to about 0.4 mm. For the patient who removes contact lenses daily, such limited movement of the lens is sufficient to permit the required fluid exchanges. For extended wear, however, it is considered desirable that there be greater lens movement during blinking to increase fluid exchange.
Adequate lens movement is perhaps the most commonly used indicator of a successful soft lens fit. Heretofore, lens movement has been controlled by varying certain parameters such as curvature of the rear surface and lens diameter. Modern soft contact lenses, however, such as the thin, low water content hydrogels used in extended wear, respond less to changes in these conventional parameters.